♦ History

The extra- to intracranial (EC-IC) bypass procedure was adopted by the international neurosurgical community after its introduction by Yasargil et al1 in 1969. The technique involved attaching the superficial temporal artery (STA) to a distal middle cerebral arterial (MCA) branch vessel, and was primarily utilized as a cerebral blood flow augmentative procedure in the treatment of cerebral ischemia caused by an occlusion or inaccessible stenosis of the internal carotid artery (ICA).

In 1985, the EC-IC Bypass Study Group2 found the procedure to be of no statistical benefit to patients when compared with aspirin treatment. Bypass was immediately discontinued as a treatment for cerebral ischemia. However, the procedure continued to be utilized for cerebral blood flow replacement as an adjunct to parent-vessel sacrifice in patients with aneurysms and tumors who had poor collateral circulation. The STA conduit and distal middle cerebral recipient were both relatively small arteries, and the volume of replacement flow was limited. Significant stroke complications have been noted in patients with apparently intact bypasses due to inadequate flow replacement. Strategies to improve flow replacement volume were subsequently developed.3 ^, 4

One important strategy to improve bypass flow is more proximal anastomosis placement on relatively large intracranial arteries. This concept of higher flow in more proximally located bypasses was mathematically confirmed by Hillen et al.5 However, when placing a conventional anastomosis proximal to one of the main cerebral arteries, such as the ICA, the MCA, the posterior cerebral artery (PCA), or the basilar artery (BA), one of the main difficulties is the obligatory temporary occlusion of the recipient artery. This is accompanied by a significant risk of brain infarction.

In attempting to avoid ischemia during proximal anastomosis attachment, the senior author (C.A.F.T.) has been working with his team on a nonocclusive anastomosis procedure since 1979. In one of the first attempts to create a nonocclusive anastomosis, the donor artery was connected for approximately three quarters of its circumference to the recipient artery wall before opening the anastomosis6 (Fig. 29.1). Scanning electromicroscopic examination of the anastomoses showed complete repair with almost perfect re-endothelialization after 3 weeks. This was a remarkable result, because against all conventions in these anastomoses adventitial and medial layers of the recipient artery were exposed in the lumen of the anastomosis.

This procedure was further developed to a fully nonocclusive anastomosis, meaning that the recipient was never occluded during anastomosis creation, using a neodymium: yttrium-aluminum-garnet (Nd:YAG) laser.7 A sapphire tip coupled to the Nd:YAG laser catheter was introduced into a side branch of a bypass graft and created a hole in the recipient artery (Fig. 29.2). After 65 rabbit experiments this technique was successfully used in one patient. However, to achieve an acceptable anastomosis, the adventitial layer and a part of the medial layer of the recipient artery had to be removed at the site of anastomosis. This is a delicate microneurosurgical procedure, which is not without risk.

Therefore, we started to use an excimer laser (first the Tui-Laser, Coherent, Inc., Santa Clara, CA, and later the Spectranetics laser, Colorado Springs, CO), which became available at the University Medical Center of Utrecht, the Netherlands, in January 1991. With this technique, removal of the adventitial and medial layers of the recipient artery was no longer necessary. Our experiments on the common carotid artery (CCA) of the rabbit showed excellent results.8 However, in the first 10 human patients, three bypasses occluded.9 We went back to the laboratory, and started experimenting on the aorta of the rabbit, which is more comparable to the human distal ICA and MCA than the rabbit CCA. It was shown that a solid excimer laser catheter tip made holes in the wall of the aorta that were severely irregular. We therefore designed a laser catheter tip that consisted of two circular layers of fine laser fibers (diameter 60 mm), arranged around a thin-walled hollow catheter with a diameter of 2.2 mm.10 This catheter has to be connected to a vacuum suction pump next to the excimer laser system (Fig. 29.3). The idea was to punch out a full-thickness disk of arterial wall, which would then be removed when the laser catheter was withdrawn. The punchedout portion of the arterial wall remains attached to the tip, because of continuous suction through the laser catheter. This would create a perfectly round anastomosis. In the first experiments, however, we did not succeed in retrieving the disk that was cut out of the arterial wall by the laser. The disk always remained attached to the wall of the artery at the two lateral sides. We hypothesized that laser light might penetrate tissue more easily if it were applied perpendicularly, and that it might have difficulties in penetrating tissue to which it was applied more obliquely.

A simple and elegant solution to this problem was found. A platinum ring with a diameter of 2.8 mm was first sutured to the arterial wall, after which the donor vein was attached to the ring plus recipient artery (Fig. 29.3). The ring created a flat surface for the laser catheter, which now could create a wide and perfectly round anastomosis. The technique was called the excimer laser–assisted nonocclusive anastomosis (ELANA) technique (Fig. 29.4). Experimental results were excellent, after which more than 400 patients were operated on using the ELANA technique.8 ^, 10 ^– 14

♦ Techniques

Extracranial-Intracranial

The most frequently performed high-flow bypass in our institution is made between the external carotid artery (ECA) extracranially and the internal carotid artery (ICA) bifurcation intracranially. As donor graft we preferably use the saphenous vein. Harvesting should be performed with minimal manipulation of the vein.15 We first make the ELANA anastomosis on the ICA using approximately 10 cm of vein graft. Since 1998, we suture the ELANA ring first to the vein graft before suturing it intracranially to the recipient artery. This reduces the number of technically difficult intracranial microsutures. After lasing the anastomosis and temporary clip placement, we make a conventional end-to-side anastomosis on the ECA using a second piece of vein graft. Subsequently, both ends of the bypass are sutured together end to end. This is performed at the spot where the bypass enters the intracranial space in a slight oblique fashion to prevent kinking of the bypass. An open conduit for the bypass is made in front of the ear, which is closed as the final step of the procedure after skin closure over the skull. We do not tunnel the bypass because we use this part of the by-pass to control for twisting or vasospasms. Moreover, we measure flow through the bypass in front of the ear until the end of the procedure.

Other extracranial inflow anastomosis spots for an EC-IC high-flow bypass include the CCA, but only in cases of ICA occlusion and hemodynamic cerebral ischemia, or the superior thyroid artery if the ECA wall is arteriosclerotic. In patients with hemodynamic cerebral ischemia who show extra- to intracranial collateral flow via the ophthalmic artery on preoperative angiographic studies, we construct a conventional end-to-side inflow anastomosis on the proximal STA.

Other outflow anastomosis spots for the ELANA technique include all cerebral arteries with a minimal diameter of 2.5 mm. If the recipient is smaller, an ELANA probably is not necessary because of collateral flow, and a conventional anastomosis can be made.

Related posts:

Carotid Endarterectomy: Decision Analysis and Surgical Technique Moyamoya: Surgical Indications and Strategies Microsurgery for Unruptured Intracranial Aneurysms Cavernoma Surgical Management of Intracranial Arteriovenous Malformations Intracranial Dural Arteriovenous Fistulas

Stay updated, free articles. Join our Telegram channel

Join